Actually, in the Java world, the "offical" Sun sanctioned ORM for a long time was J2EE Entity Beans. But it never was very popular because it was a pile of crap.
When it was obvious that basically everyone moved on to Hibernate, Sun basically took Hibernate's API, renamed it to JPA, and called that the new standard.
That kind of stuff probably won't happen in the .NET community. First of all, no matter how "broken" Java's community process might be, .NET has NO community process at all. Also I generally notice .NET developers will pick up ANY technology that has Microsoft's name on it, no matter how crappy or poorly designed it is. They'll even say stuff that basically amounts to "this is a pile of crap, but it's written by Microsoft, so lets use it!".
This is not exactly .NET developers fault either. The whole "merit system" Microsoft has in place (eg: the MVP program) ensures the best way to get far is to parrot whatever the army of Microsoft evangelists are saying. That's why somone like Ayende has doesn't have an MVP despite being involved in writing 5+ widely used .NET libraries, and random idiots with obsecure blogs who copy/paste Microsoft press releases are.
That's why I really think NHibernate or other community ORMs stand no chance in the long run. It's obvious think Microsoft doesn't take the .NET community seriously or even acknoledge their existance. And .NET is so top down command and controlled which makes it even worse. .NET developers are too entralled with with millions (or billions?) of dollars in developer evangelism money being used to push the latest half-baked solution to a problem that has been solved already, better, outside of Microsoft's offices. So crappy technology is allowed to dominate just because of this. It's sad to watch.
And yes, I was being nice by saying Microsoft has a "business reason" for this. But it's probably actually just typical corporate self-destructive behavior, driven by office politics and job security concerns. It seems the words "code complete" often lead to the words "lay off".